In the use of elevated platforms for supporting people and/or cargo, it is generally desirable to provide a protective enclosure for confining the people and/or cargo on the supporting surface of the platform. Platform lifting machines, such as mobile lift mechanisms, having platforms which are vertically elevated, are known in the art and are provided with railing structures to confine the people on the platform. It is desirable for such railings to be positioned at a sufficient height above the edges of the platform to inhibit people from falling from the platform. It is also desirable for the railing to be sufficiently high and rigid to withstand and restrain outward forces applied to the railing, for example, when people lean against the railing.
Platform lifting machines are used at a wide variety of applications in buildings, particularly office and government buildings. The platform lifting machines are frequently transported to different areas in the buildings through door ways having limited vertical clearance or from floor to floor on freight elevators having limited access openings. When moving the lift mechanism from one area to another, the height of the platform lifting machine must be less than the vertical clearance of the door frame or other opening between areas. The presence of a railing or other protective structure above the perimeter of the platform contributes significantly to the overall height of the lifting machine. In order to provide the ability to reduce the height of the platform lifting machine for the purpose of passing through doorways and other limited access openings, lifting machines have been designed with various types of collapsible or removable railings, such as inwardly or outwardly folding railings, telescoping railings, or completely removable railings.
All of the prior art attempts to reduce the height of lifting machines have not produced satisfactory solutions and all have possessed distinct disadvantages. For example, in the use of removable railings, workers using the lifting machine may neglect to replace the railing on the platform or may improperly fit parts together prior to using the lift machine. Railings which fold inwardly or outwardly relative to the platform area have been found to be awkward to use by persons standing upon the platform. Additionally, folding railings and telescoping railings have relied upon removable fasteners, such as removable lock pins, in order to secure the railings in a desired position. As in the use of removable railings, workers using such lifting machines, may neglect to replace the locking pins, thereby being exposed to the risk of injury because the railing is not secure to prevent falling from the platform.
It would be desirable to provide a protective railing structure for platform lifting machines that would be easy to reduce in height when desired and would be conducive to easy and safe replacement to its protective position when the platform is in use. It would also be desirable to provide a protective railing structure that would be particularly resistant to failure when receiving the force of a person falling against the railing while using the platform.